Environmentally friendly hydrofracturing friction reducer for harsh conditions

ABSTRACT

A composition for an environmentally friendly hydrofracturing friction reducer product can be synthesized. A method for synthesis of a friction reducer emulsion can include using gas-to-liquid synthesized oil as a continuous phase in invert emulsion polymerization. The composition can be optimized by using a suitable amount of salt tolerant monomer for the best performance with salt tolerant features. Various inverting agents can be utilized for the self-inverting in brine with good product stability. The optimized friction reducer can be used in weighted brine hydrofracturing.

FIELD

The disclosure relates generally to hydraulic fracturing. The disclosurerelates specifically to friction reduction in hydraulic fracturing.

BACKGROUND

Hydraulic fracturing is widely used in shale/tight reservoirs beforeproduction to increase production rate, which creates small conductiveflow paths for hydrocarbon to flow from low permeability reservoirs. Oneof the most important aspects in successful hydraulic fracturing isdevelopment of highly effective fracturing fluids. Slickwater systemshave become one of the most common used fracturing fluids over the pastdecade.

Slickwater systems consist of water, proppant, biocide, scale inhibitor,and a friction reducer. In a slickwater hydrofracture operation process,fracturing fluid is pumped at very high speed to carry proppant andcreate fracturing. A friction reducer is the key component for thesuccess of slickwater fracturing. Friction reducers can effectivelyreduce the pumping pressure at the surface and increase the injectionrate by changing the turbulent flow to laminar flow, which reduces thefluid friction and reduces the energy cost. The slickwater fluid shows arelatively low viscosity during fracture extension and is easy to flowback.

There are mainly two kinds of friction reducer: dry powder form andemulsion form with a mineral oil base. The dry powder form is moreeffective, which saves on shipping cost. However, it is very hard todissolve the powder friction reducer on the well site. It requiresspecial equipment to prepare the solution on the hydraulic fracturingsite. Thus, it takes a larger footprint and space is precious at thesite. The emulsion form friction reducer can be used by an on-the-flyaddition method. The drawback of the emulsion form friction reducer isthat it is less efficient due to the presence of 70-80% of water and oilin the formulation. Another drawback of the emulsion form frictionreducer is that it is environmentally unfriendly due to the mineral oilin the formulation. To save on the cost of water, more and more flowbackand produced water are used as fracturing fluid. The flowback andproduced water contain high concentrations of brine. The traditionalfriction reducers are salt sensitive and will fail when utilized withhigh concentrations of brine. There is a need for a new friction reducerto solve these problems.

Another trend is stimulation of more high pressure, ultra-deep, tightoil and gas reservoirs. These situations are challenging due to thepressure limitation of completion equipment and surface equipment. Theconventional fracturing fluid density is around 1 gram/ml, which cannotcreate enough downhole pressure with the current available technologyand equipment. To increase the fracturing pressure and decrease thewellhead pressure, one obvious strategy is to use a high-density fluidby adding salt to make a weighted fracture fluid, which will increasethe column pressure. However, the friction of high-density brine is muchhigher than fresh water in high pumping rate. The friction of fluidcounteracts the increasing of downhole pressure by brine. The frictionreducer can be used to reduce the friction pressure loss in conventionalfresh water fracturing. In a saturated brine situation, the conventionalfriction reducers are not effective because the very high ion strengthhinders the hydration process. The conventional friction reducers losesome of their effectiveness with shear. There is a need for a newfriction reducer that can work in a weighted fracturing fluid. Thisensures operation safety and creates more downhole pressure for betterfracturing.

There is a need for a friction reducer that uses a biodegradable baseoil which is environmentally friendly. The friction reducer needs tofunction in flowback water, produced water, and the harshestcondition—saturated weighted brine fraction fluid. The friction reducershould also function in high temperature conditions which are verycommon in ultra-deep wells. The new friction reducer needs to be shearstable at high pumping rates.

SUMMARY

An embodiment of the disclosure is a composition for a friction reducerfor a wellbore comprising an oil phase comprising about 10-70 partsgas-to-liquid synthesized base oil and about 1-20 parts emulsifiercomprised of sorbitan monostearate and a sorbitan fatty acid esterethoxylate surfactant; an aqueous phase comprising about 5-35 partsmonomers comprising an acrylamide (AM), a2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), an acrylic acid(AA), and a water; and about 0.001 to 1 parts of an initiator selectedfrom the group comprising ammonium peroxodisulfate, tert-butylhydroperoxide, dimethane sulfonyl peroxide, potassium persulfate,benzoyl peroxide, lauroyl peroxide, sodium persulfate,2,2′-Azobis(isobutyronitrile),2,2′-Azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-Azobis(2,4-dimethylvaleronitrile), Dimethyl2,2′-azobis(2-methylpropionate), 2,2′-Azobis(2-methylbutyronitrile),1,1′-Azobis(cyclohexane-1-carbonitrile),2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride,2,2′-Azobis(2-methylpropionamidine)dihydrochloride,2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate,diethyl 2,2′-azobisisobutyrate, dimethyl 2,2′-azobisisobutyrate,2-methyl 2′-ethyl azobisisobutyrate, dimethyl 2,2′-azobis(isobutyrate),2,2′-Azobis[2-(2-imidazolin-2-yl)propane],2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide],4,4′-Azobis(4-cyanovaleric acid), or combinations thereof. In anembodiment, the amount of the gas-to-liquid synthesized base oil isabout 20 parts. In an embodiment, the emulsifier is sorbitanmonostearate and a sorbitan fatty acid ester ethoxylate surfactant andthe amount of the emulsifier is about 2 parts. In an embodiment, theamount of the AM is about 20 parts, the amount of the AMPS is about 2parts, and the amount of the AA is about 8 parts. In an embodiment, theamount of the water is about 40%. In an embodiment, the initiator is2,2′-Azobis(isobutyronitrile) and the amount of the2,2′-Azobis(isobutyronitrile) is about 0.01 parts. In an embodiment, thepH of the aqueous solution is 6-8. In an embodiment, the compositionfurther comprises a surfactant with an HLB of at least about 10 at about2 wt. %.

An embodiment of the disclosure is a method of preparing a frictionreducer for a wellbore comprising preparing an oil phase by mixing about10-70 parts gas-to-liquid synthesized base oil with about 1-20 partsemulsifier comprising sorbitan monostearate and sorbitan fatty acidester ethoxylate surfactant; mixing the resulting oil phase until it isclear; preparing an aqueous phase comprising about 5-35 parts ofmonomers comprising mixing an AM, an AMPS, an AA, and a water andadjusting the pH to 6-8; mixing the oil phase with the aqueous phase toform a mixture; emulsifying the resulting mixture to form an emulsionwith a viscosity of greater than 200 cP; purging the emulsion withnitrogen for 30 minutes; adding about 0.001-1 parts an initiatorselected from the group comprising ammonium peroxodisulfate, tert-butylhydroperoxide, dimethane sulfonyl peroxide, potassium persulfate,benzoyl peroxide, lauroyl peroxide, sodium persulfate,2,2′-Azobis(isobutyronitrile),2,2′-Azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-Azobis(2,4-dimethylvaleronitrile), Dimethyl2,2′-azobis(2-methylpropionate), 2,2′-Azobis(2-methylbutyronitrile),1,1′-Azobis(cyclohexane-1-carbonitrile),2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride,2,2′-Azobis(2-methylpropionamidine)dihydrochloride,2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate,diethyl 2,2′-azobisisobutyrate, dimethyl 2,2′-azobisisobutyrate,2-methyl 2′-ethyl azobisisobutyrate, dimethyl 2,2′-azobis(isobutyrate),2,2′-Azobis[2-(2-imidazolin-2-yl)propane],2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide],4,4′-Azobis(4-cyanovaleric acid), or combinations thereof to theemulsion; increasing a temperature of the emulsion from room temperatureto 40° C. over a period of about 30 minutes; incubating the emulsion forabout 3 hours at 40° C.; incubating the emulsion for about 1 hour at 50°C.; and incubating the emulsion for about 1 hour at 70° C. In anembodiment, the method further comprises charging the emulsion into aglass jacketed kettle equipped with a paddle stirrer and thermometer. Inan embodiment, the amount of the gas-to-liquid synthesized base oil isabout 20 parts. In an embodiment, the emulsifier is sorbitanmonostearate and a sorbitan fatty acid ester ethoxylate surfactant andthe amount of the emulsifier is about 2 parts. In an embodiment, theamount of the AM is about 20 parts, the amount of the AMPS is about 2parts, and the amount of the AA is about 8 parts. In an embodiment, theamount of the water is about 40%. In an embodiment, the initiator is2,2′-Azobis(isobutyronitrile) and the amount of the2,2′-Azobis(isobutyronitrile) is about 0.01 parts. In an embodiment, themethod further comprises a surfactant with an HLB of at least about 10at about 2 wt. %.

An embodiment of the disclosure is a method of use comprising pumping athigh speed the composition above into a wellbore. In an embodiment, thecomposition reduces friction. In an embodiment, the composition is salttolerant. In an embodiment, the composition is biodegradable.

An embodiment of the disclosure is a composition for a friction reducerfor a wellbore comprising an oil phase comprising about 10-70%gas-to-liquid synthesized base oil and about 1-20% emulsifier comprisedof sorbitan monostearate and a sorbitan fatty acid ester ethoxylatesurfactant; an aqueous phase comprising about 5-65% monomers comprisingacrylamide (AM), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS),acrylic acid (AA), and water; and AIBN. In an embodiment, the amount ofthe gas-to-liquid synthesized base oil is about 20%. In an embodiment,the amount of the emulsifier is about 2%. In an embodiment, amount ofthe AM is about 20%, the amount of the AMPS is about 2%, and the amountof the AA is about 8%. In an embodiment, the amount of the water isabout 40%. In an embodiment, the amount of the AIBN initiator is about0.01%. In an embodiment, the pH of the aqueous solution is 6-8. In anembodiment, the composition further comprises a linear alcoholethoxylate inverting surfactant at about 2 wt. %.

An embodiment of the disclosure is a method of preparing a frictionreducer for a wellbore comprising preparing an oil phase by mixing about10-70% gas-to-liquid synthesized base oil with about 1-20% emulsifiercomprising sorbitan monostearate and sorbitan fatty acid esterethoxylate surfactant; mixing the resulting oil phase until it is clear;preparing an aqueous phase comprising about 5-45% monomers comprisingmixing AM, AMPS, AA, and water and adjusting the pH to 6-8; mixing theoil phase with the aqueous phase to form a mixture; emulsifying theresulting mixture to form an emulsion with a viscosity of greater than200 cP; purging the emulsion with nitrogen for 30 minutes; adding about0.001-1% AIBN as an initiator to the emulsion; increasing thetemperature from room temperature to 40° C. over a period of about 30minutes; incubating the emulsion for about 3 hours at 40° C.; incubatingthe emulsion for about 1 hour at 50° C.; and incubating the emulsion forabout 1 hour at 70° C. In an embodiment, the method further comprisescharging the emulsion into a glass jacketed kettle equipped with apaddle stirrer and thermometer. In an embodiment, the amount of thegas-to-liquid synthesized base oil is about 20%. In an embodiment, theamount of the emulsifier is about 2%. In an embodiment, the amount of AMis about 20%, the amount of AMPS is about 2%, and the amount of AA isabout 8%. In an embodiment, the amount of water is 40%. In anembodiment, the amount of AIBN initiator is about 0.01%. In anembodiment, the method further comprises adding a linear alcoholethoxylate inverting surfactant at about 2 wt. %.

An embodiment of the disclosure is a method of use comprising pumping athigh speed the composition of claim 1 into a wellbore. In an embodiment,the composition reduces friction. In an embodiment, the composition issalt tolerant. In an embodiment, the composition is biodegradable.

The foregoing has outlined rather broadly the features of the presentdisclosure in order that the detailed description that follows may bebetter understood. Additional features and advantages of the disclosurewill be described hereinafter, which form the subject of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and otherenhancements and objects of the disclosure are obtained, a moreparticular description of the disclosure briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the disclosure and are therefore notto be considered limiting of its scope, the disclosure will be describedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 depicts the results of friction reduction test of FR1, FR2, FR3,or FR4 in Houston tap water (HTW), 0.25 gallons per thousand gallons(GPT).

FIG. 2 depicts the results of a friction reduction test of FR1 and FR2with 1.4 g/ml sodium bromide.

FIG. 3 depicts the results of a friction reduction test of FR1 with 1.3g/ml sodium nitrate at 0.25 GPT and 0.50 GPT.

FIG. 4 depicts the equipment used to synthesize the friction reducer inan embodiment of the disclosure.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentdisclosure only and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of various embodiments of thedisclosure. In this regard, no attempt is made to show structuraldetails of the disclosure in more detail than is necessary for thefundamental understanding of the disclosure, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the disclosure may be embodied in practice.

The following definitions and explanations are meant and intended to becontrolling in any future construction unless clearly and unambiguouslymodified in the following examples or when application of the meaningrenders any construction meaningless or essentially meaningless. Incases where the construction of the term would render it meaningless oressentially meaningless, the definition should be taken from Webster'sDictionary 3^(rd) Edition.

As used herein, the term “copolymer” means and refers to polymerscontaining two monomers and any combination of polymers, e.g.,terpolymers, tetrapolymers, and the like.

A synthesis method and composition for environmentally friendlyhydrofracturing friction reducers are disclosed. In an embodiment, amethod for synthesis of a friction reducer emulsion includes usinggas-to-liquid synthesized oil as a continuous phase in invert emulsionpolymerization. In another embodiment, the composition was optimized byusing a suitable amount of salt tolerant monomer for the bestperformance with salt tolerant features. The method also includes theselection of inverting agents for the self-inverting in brine with goodproduct stability.

Disclosed herein is a new friction reducer, a specially designedformulation with biodegradable base oil. This new friction reducer shows78% friction reduction in fresh water with 0.025% dosage, which willeffectively save the hydraulic fracturing operation cost. It also hasexcellent friction reduction efficiency in weighted brine. It is stablein high pressure and high temperature downhole conditions. The hydrationtime is only a few seconds. It can be added by an on-the-fly method.Another advantage of the new friction reducer is that it is quite shearstable.

Novel features of the friction reducer include:

-   -   A biodegradable oil is used as the base oil. The new friction        reducer is environmentally friendly. It ultimately improves the        environmental impact of a well operation.    -   The new friction reducer uses a specially optimized        copolymerization technique, which makes it highly salt-tolerant.        It can be used in weighted water (saturated brine), flowback        water, and produced water.    -   The new friction reducer hydrates very quickly when added to        water. It uses specially optimized inverting agents and a        combination of stability surfactants. It can effectively reduce        the friction. The inverting agents are also biodegradable.    -   The new friction reducer is stable at high temperature due to        its special monomer. Therefore, it can be used in deep wells        with high temperature.    -   The new friction reducer is shear stable due to the special        monomer. It can be pumped at very high speed.

Advantages of the friction reducer include:

-   -   The new friction reducer provides the oilfield industry a        cost-effective solution of reducing produced water disposal.    -   The present subject matter provides similar or better        performance compared with known formulations having higher        polymer loadings.    -   This technology also provides additional benefits, such as        reduced formation damage, and decreased operational costs.

A new kind of environmentally friendly and salt-tolerant frictionreducer was synthesized. The friction reducer can effectively reduce thefriction in hydraulic fracturing applications in various types of waterincluding but not limited to fresh water, produced water, flowbackwater, and weighted brine.

The new friction reducer uses a biodegradable oil as the base oil, whilethe conventional friction reducers use saturated alkanes, branchedalkanes, naphthenes (homo-cyclics and hetero-cyclics). These aromaticsare toxic to the environment.

Slickwater fracturing has been proven to be a very effective method toincrease the recovery of tight gas and shale gas reservoirs. In thecurrent slickwater fracturing process, the fluid volumes have beendramatically increased. The produced water and flowback water normallyhave very high total dissolved solids (TDS). This is a huge challengefor a conventional friction reducer because the ions in the fluid hinderthe inversion of the invert emulsion. The active polymer cannot bereleased from the oil phase, thus the efficiency of a conventionalfriction reducer is quite low in these cases. There are some strategiesto process the produced water to remove ions. However, the process isvery time consuming and the cost is high. In a weighted fraction fluidsystem, it is impossible to remove the ions since they ions are used toincrease the density of the fraction fluid. The conventional frictionreducer will fail in these situations.

The new friction reducer resolves the salt-tolerant problem by usingspecially synthesized oil, which can easily release the polymer in highTDS fluid. To enhance the salt-tolerant feature, the monomers were alsospecially optimized. A suitable ratio of ions and salt-tolerant monomerprovides the best balance of performance in brine and stability. Thenewly designed friction reducer resolves the environmental problem,salt-tolerant problems, thermostability problems, and performanceproblems at a low dosage.

In an embodiment, the new friction reducer was synthesized by aninverse-emulsion method. The inverse-emulsion is water-in-oil, having anoil phase (O) and an aqueous phase (A). The inverse emulsion uses thebiodegradable synthesized oil as a continuous phase and the aqueousphase as a dispersed phase of distinct drops in the continuous oilphase. In an embodiment, the water-soluble polyacrylamide copolymer isin the water phase. In an embodiment, the surfactant was used in thesystem to help disperse the water in oil phase. In an embodiment, theO:A ratio can be in the range of 2:1 to about 1:10. In an embodiment,the water-soluble polyacrylamide copolymer is present in an amount fromabout 1 to about 60 weight percent of the water-in-oil emulsion. In anembodiment, the water-soluble polyacrylamide copolymer includes fromabout 1 to about 70 weight percent of one or more ionic monomers,wherein the amount is by total weight of the polymer. In an embodiment,an inverting surfactant can be added to the system to speed up thehydration rate when mixing with water. In an embodiment, the invertingof the inverse emulsion can be done by adding it to water at from about0.1 to about 20 gallons of water-in-oil emulsion per thousand gallons ofwater to form a friction reducing treatment solution.

As used herein, the term “copolymer,” is not limited to polymerscontaining two monomers, but also includes any combination of polymers,e.g., terpolymers, tetrapolymers, and the like.

In an embodiment, the inverse emulsion includes an oil phase, an aqueousphase, and surfactants.

In an embodiment, the oil phase (O) and the aqueous phase (A) ratio(O:A) can be as low as 1:9 based on the volume of each phase, but theemulsion will be not very stable. In some cases, the O:A ratio can beabout 1:8, in some cases at least about 1:6, in other cases at leastabout 1:4, in other cases can be up to about 2:1, in some cases up toabout 1:1, and in other cases up to about 1:2. When the O:A ratio ishigh, the cost will be high, it is hard to invert, and the hydrationtime will be long. In a typical pumping process, the fluid takes 3minutes to reach the bottom of the well. If the hydration time is toolong, the friction reducer will not have a friction reduction effect atall.

The conventional invert-emulsion polyacrylamide friction reducer useinert hydrophobic liquid as the continuous phase, which can be mineraloil, kerosene, paraffin oil, naphthenes, cycloparaffins or hydrogenatedbenzenes, aromatic hydrocarbons, xylene, toluene, or branch-chainhydrocarbons. The flowback wastewater contains the base oil of frictionreducer. Therefore, hydrocarbon contamination in the environment is avery serious problem. Some of friction reducers have high cyclicaromatic hydrocarbon contents. High cyclic aromatic hydrocarbons areubiquitous environmental pollutants. Many cyclic aromatic hydrocarbonsare toxic, which have mutagenic/carcinogenic effects. Most of cyclicaromatic hydrocarbons are lipid soluble and absorbed from thegastrointestinal tract of mammals. They are rapidly absorbed by a widevariety of tissues with a marked tendency for localization in body fat.These kinds of chemicals pose a serious threat to the human andenvironmental health. The cyclic aromatic hydrocarbons are consideredresistant to degradation due to their low reactivity. The United StatesEnvironmental Protection Agency (EPA) has classified these compounds aspriority contaminants of natural resources. Aromatic contents should beavoided in hydrofracturing fluids if possible. In a new trend,branched-chain hydrocarbons are widely used. However, mostbranched-chain hydrocarbons have long degradation periods, and recentstudies show high-accumulated concentrations in soil, aquatic, andatmospheric environments. Environmental pollution caused by hydrocarbonsin flowback water is of great concern because those hydrocarbons aretoxic to all forms of life.

Although bacteria are challenged by the hydrophobicity of hydrocarbons,known to cause toxic effects on the bacteria and restrict absorption ofthe hydrocarbons into the bacteria, bacteria are able to very slowlydegrade aliphatic hydrocarbons via both aerobic and anaerobic pathways.Branched hydrocarbons and cyclic hydrocarbons can also be digested bybacteria to some extent at an extremely slow speed. The molecular weightand structure of the hydrocarbon highly affects the uptake/degradationspeed. For example, high molecular weight hydrocarbons are much harderto uptake by bacteria due to the slow dissolution and difficulty ofsolubilization. Thus, the high molecular weight hydrocarbons aredegraded much slower than small molecular weight hydrocarbons.

Disclosed herein are environmentally safe, biodegradable oils for use asa base oil for in the synthesis of a friction reducer, making thefriction reducer environmentally friendly. The biodegradable oil caninclude but is not limited to including synthetic, natural, or modifiedoils such as Castrol biodegradable oil (BIO OIL RD 100 & BIO BOLT),Biosynthetic™ Base Oils from Biosynthetic Technologies (BT), BIO-BASE®Synthetic oil (BIO-BASE® 100LF, BIO-BASE® 200, BIO-BASE® 300, BIO-BASE®365, BIO-BASE® 625, BIO-BASE® 628) from Shrieve, G-OIL from Green EarthTechnologies, Inc, Klüber Summit DSL 32, 46, 68 and 100, BiodegradableHydraulic Oil from Belray, the BIO NATUR range of biodegradable oil fromthe Condat group, Hydro Safe's® readily biodegradable, non-toxichydraulic oils, and vegetable oils such as coconut oil, corn oil,rapeseed oil, soybean, canola oil and the like. Bio-base oil utilizes anumber of synthetic and hydrocarbon chemistries that deliver a range ofperformance benefits, including low or undetectable aromatic contents,excellent kinematic viscosities, low pour points, and improvedoccupational hygiene profiles, as well as enhanced biodegradability andmarine toxicology.

In various embodiments, the oil continuous phase in the inverse emulsioncan be in the range of 10-70% based on the weight of the emulsion. Insome embodiments, the oil can be 16%; in other embodiments, the oil isat least 18%. In other cases, the oil phase should be no less than 22%based on the weight of emulsion. In some cases, the oil phase can be30%; in some cases, up to 40%; in other cases, up to about 70%. The oilphase provides a stable continuous phase for the emulsion. When the oilpercentage is too low, the emulsion will be not be stable in some cases.When the oil percentage is too high, the cost will be high, the activeloading will be less, and the performance will be bad. The optimizationof a suitable oil phase is very important for the best friction andstability performance.

In order to make a water-in-oil emulsion, one or more lowhydrophilic-lipophilic balance (HLB) surfactants should be used todisperse the water phase in the oil phase. Surfactants are moleculesthat have a hydrophobic (oil soluble) and an effective hydrophilic(water soluble) portion. Surfactants act as emulsifiers by lowering theinterfacial tension and decreasing the coalescence of disperseddroplets. The HLB method has been used to determine the suitablenonionic surfactants to be used as emulsifiers. In some embodiments, theideal HLB range for the inverse emulsion is 4-6. In other embodiments,the HLB can be in the range of 3-9. In some cases, the preferred HLB is6-8 depend on the oil type and the formulation of the emulsion. A blendof high and low HLB surfactants is often used to achieve the desiredvalue in part because of demonstrated effectiveness and efficiencies inpacking at the interface. The oil phase and the ratio of oil to waterhighly affects the required HLB. However, it does not mean theemulsifier or blend having the specific HLB value will work. The rightchemistry is also very important for the stable emulsion.

Many types of surfactants can be used in the friction reducer. In anembodiment, the surfactants include, but are not limited to, sorbitanfatty acid esters, ethoxylated sorbitan fatty acid esters,polyethoxylated sorbitan fatty acid esters, the ethylene oxide and/orpropylene oxide adducts of alkylphenols, the ethylene oxide and/orpropylene oxide adducts of long chain alcohols or fatty acids, mixedethylene oxide/propylene oxide block copolymers, and alkanolamides.Examples include, but are not limited to, sorbitan monooleate, sorbitantrioleate, sorbitan tristearate, sorbitan monostearate, sorbitanmonopalmitate, sorbitan monolaurate, PEO(20)-sorbitan trioleate,PEO(20)-sorbitan mono-oleate, PEO(20) sorbitan tristearate,PEO(20)-sorbitan monostearate, PEO(20) sorbitan monopalmitate, PEO(20)sorbitan monolaurate. Polymeric surfactants, such as modified polyestersurfactants and maleic anhydride-substituted ethylene copolymers, canalso be used as emulsifiers. In an embodiment, the emulsifier is a fattyacid esters, ethoxylated sorbitan fatty acid esters, or a surfactant andtheir mixer which have an HLB value in 4-10 range.

A mixture of surfactants, rather than a single surfactant, can be usedto make the suitable HLB emulsifiers. The concentration of emulsifiercan be from about 1% to about 20% by weight, based on the total weightof the emulsion. Any surfactant system, which effectively disperses anaqueous phase into a hydrophobic phase, can be used. The emulsifier canbe present at a level of at least 1%, in some cases at least about 2%and in other cases at least about 3% based on the weight of theemulsion. When there is too little emulsifier in the system, theemulsion will not be stable and the oil and water phase will separate.The emulsifier can be up to 20% in some cases and up to 10% in othercases. In an embodiment, the amount of emulsifier is from 2% to 10%based on the weight of the emulsion.

In an embodiment, the inverse-emulsion polymers are homo or copolymersof acrylamide and/or other monomer. In an embodiment, monomers used inthe acrylamide copolymerization include nonionic, cationic, and anionicmonomers which will polymerize with acrylamide and yield a water-solublecopolymer. In an embodiment, non-limiting monomers include, but are notlimited to, acrylamide, the free acids and salts of: acrylic acid;methacrylic acid; acrylamidoglycolic acid; 2-acrylamido-2-methylpropanephosphonic acid; 2-acrylamido-2-methyl-1-propanesulfonic acid;3-allyloxy-2-hydroxy-1-propanesulfonic acid; vinylphosphonic acid;maleic acid; itaconic acid; styrene sulfonic acid; vinylsulfonic acid;ethyl acrylate; acrylonitrile; methylmethacrylate,diallyldimethylammonium chloride, dimethylaminoethylmethacrylate,dimethylaminoethylmethacrylate quaternaries, N-vinyl pyrrolidone,styrene, N,N-dimethylacrylamide, ethyl acrylate, methyl acrylate,ethylmethacrylate, and mixtures of any of the foregoing and the like.The resultant polymer can be non-ionic, cationic, anionic, oramphoteric.

In an embodiment, almost all of the monomers will convert to polymers bythe end of the reaction. In an embodiment, the composition of the finalpolymer will be about the same as the composition of the monomermixture. The amount of monomers will determine the polymer concentrationin the final emulsion. If the concentration of polymer is low, the totalweight of friction reducer will be high in the final application, whichis uneconomical due to the high shipping cost. Another problem of a lowpolymer concentration is that the final product molecular weight will beaffected, and the reaction speed will be low. When the concentration ofactive polymer is too high, the emulsion system will not be stable. Thereaction speed will be high because the monomer will have a greaterchance to react due to the high concentration. It is hard to control thereaction in this situation. In an embodiment, the amount of monomers isat least 10 weight percent, in some cases at least about 5 weightpercent, and in other cases at least about 20 weight percent based onthe weight of the emulsion. In other embodiments, the amount of monomerscan be up to about 35, in some cases up to about 30, in other cases upto about 25 percent based on the weight of the emulsion. In anembodiment, the preferred amount of monomers in the aqueous phase of thewater-in-oil emulsion can be in the range of 20-30%. The percentage ofmonomers can be any value or can range between any of the values recitedherein.

In an embodiment, both oil-soluble and water-soluble initiator can beused for the radical polymerization depending on the particular needs ofthe system. Suitable initiators include, but are not limited to,ammonium peroxodisulfate, tert-butyl hydroperoxide, dimethane sulfonylperoxide, potassium persulfate, benzoyl peroxide, lauroyl peroxide,sodium persulfate, 2,2′-Azobis(isobutyronitrile),2,2′-Azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-Azobis(2,4-dimethylvaleronitrile), Dimethyl2,2′-azobis(2-methylpropionate), 2,2′-Azobis(2-methylbutyronitrile),1,1′-Azobis(cyclohexane-1-carbonitrile),2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride,2,2′-Azobis(2-methylpropionamidine)dihydrochloride,2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate,diethyl 2,2′-azobisisobutyrate, dimethyl 2,2′-azobisisobutyrate,2-methyl 2′-ethyl azobisisobutyrate, dimethyl 2,2′-azobis(isobutyrate),2,2′-Azobis[2-(2-imidazolin-2-yl)propane],2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide],4,4′-Azobis(4-cyanovaleric acid), and combinations thereof.

In an embodiment, the amount of initiator in the emulsion can be fromabout 0.001 to 1% by weight percentage and in some cases from 0.01% to0.5% by weight of the monomer mixture. In an embodiment, the amount ofinitiator in the emulsion is 0.01-0.1%. In an embodiment, redoxinitiator systems can also be used. The use of a redox initiator systemcan lower the reaction temperature. A higher molecular weight polymercan be produced with good control of the reaction. In an embodiment, theredox systems used contain persulfates or hydroperoxides as oxidants andascorbic acid, formaldehyde sulfoxilate, tetramethyl ethylene diamine,or sodium metabisulfites as reducing agents.

In some embodiments, the polymerization may have an initiationtemperature of about 15° C. and proceed adiabatically. In otherembodiments, the polymerization reaction can be carried out isothermallyat a temperature of about from 35° C. to about 60° C. In an embodiment,the temperature is in the range of about 40-45° C. In an embodiment, atthe final step, the reaction temperature can reach up to 70° C. toremove the unreacted monomers. In an embodiment, 60° C. will generallybe an upper limit for the inverse emulsion polymerization.

In an embodiment, the free-radical inverse emulsion polymerization isconducted as follows. An aqueous solution of the monomers is made bymixing monomers in water and the pH of the solution is adjusted to thepH 6-8 range. The oil phase is made by mixing the emulsifiers with theoil. The aqueous phase is then homogenized into the oil phase byhomogenizers or high-speed agitators. The monomer emulsion is thensubjected to free radical polymerization by adding an initiator orheating under nitrogen purging. Optionally, a high HLB invertingsurfactant can be added to enhance the inversion of the emulsion whenmixed with water. Any technique to prepare the inverse emulsions knownto those skilled in the art can be used.

In an embodiment, the surfactants utilized to enhance the inversion ofthe water-in-oil emulsion when the emulsion is added to water arehydrophilic, preferably with an HLB of at least about 10, and include,but are not limited to, linear and branched alcohol ethoxylates,ethoxylated sorbitans, octyl or nonylphenol ethoxylates, ethoxylatedcastor oil, ethoxylated octyl or nonyl phenol formaldehyde resins,dioctyl esters of sodium succinate and the like. In an embodiment,ethoxylated octyl or nonyl phenols can be used.

In an embodiment, the final acrylamide polymers produced can have amolecular weight of from several hundred thousand to several tens ofmillions. In an embodiment, the friction reducer will have molecularweights ranging from 1 to 30 million. In an embodiment, the molecularweight is from 5 to 20 million. In an embodiment, the polyacrylamidecopolymer has a molecular weight of approximately 10 million.

Disclosed herein is an environmentally friendly friction reducer and asynthesis method for preparing the environmentally friendly frictionreducer. The friction reducer can be used in hydrofracturing to treat asubterranean formation in a method that includes, but is not limited to,providing a water-in-oil emulsion synthesis route and formulation of afast inverting friction reducer in a saturated brine solution.

In an embodiment, the friction reducer can be used in fresh water,flowback water, or produced water. In an embodiment, the frictionreducer can be used in weighted water, which contains concentrated brineto increase the fluid density. In an embodiment the concentrated brineincludes, but is not limited to, sodium nitrate, sodium bromide, orsodium formate.

EXAMPLES

Herein, all parts and percentages are weight percent unless otherwisespecified.

Example 1—Friction Reducer 1 (FR 1) (BIO-BASE® Oil, Salt TolerantMonomers)

A terpolymer of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS),acrylamide (AM) and acrylic acid (AA) invert emulsion is prepared by afree radical polymerization method. The oil phase is made by mixing 20parts gas-to-liquid synthesized BIO-BASE® oil, available commerciallyfrom Shrieve Chemical Company, with 2 parts emulsifier. The emulsifieris made by mixing Span® 60 (sorbitan monostearate) with Tween® 61(sorbitan fatty acid ester ethoxylate) surfactant providing an HLB of6.5. The resulting oil phase is mixed by an overhead mixer. A clear oilphase solution is ready for emulsification. The aqueous phase is made bymixing 20 parts AM, 2 parts AMPS, 8 parts AA, and 40 parts water. The pHof aqueous solution is adjusted to pH 6-8 by adding sodium hydroxide.The oil phase is mixed with aqueous phase by a high-speed mixer. Theresulting mixture is emulsified until the emulsion viscosity increasesto more than 200 cP. The resulting water-in-oil emulsion is charged intoa glass-jacketed kettle equipped with a paddle stirrer and thermometer.The emulsion is purged with nitrogen for 30 minutes to remove oxygen andthen 0.01 parts 2,2′-azobis(isobutyronitrile) (AIBN) as an initiator isadded to the emulsion. The temperature is increased from roomtemperature to 40° C. in 30 minutes. The polymerization is allowed toproceed for 3 hours at 40° C. and for another hour at 50° C. Thetemperature is then kept at 70° C. for one more hour. Next, 2 wt. % of alinear alcohol ethoxylate inverting surfactant, containing 12-15 carbonunits and having an HLB of 13.3, is slowly added dropwise to theemulsion.

The resulting emulsion dissolved easily in water to provide a polymersolution. The inverting of an inverse emulsion can be done by adding itto water by an on-the-fly method at from about 0.1 to about 10 gallonsof emulsion polymer per thousand gallons of water to form a frictionreducing treatment solution. A 1% solution of an inverse emulsionpolymerization product will give a viscosity of 600-1000 cp. Somemechanical energy typically facilitates inversion of this product in afew seconds.

Example 2—FR 2 (BIO-BASE Oil, No Salt Tolerant Monomers)

A copolymer of acrylamide (AM) and acrylic acid (AA) invert emulsion isprepared by similar method as the example 1 except no AMPS was added.The oil phase is made by mixing 20 parts gas-to-liquid synthesizedBIO-BASE® oil with 2 parts emulsifier, which is made by mixing Span® 60with Tween® 61 surfactant that provided an HLB of 6.5. An overhead mixerwas used to mix the resulting oil phase. A clear oil phase solution isready for emulsification. The aqueous phase is made by mixing 20 partsAM, 10 parts AA, and 40 parts water. The pH of the aqueous solution istuned to pH 6-8 by adding sodium hydroxide. The oil phase is mixed withthe aqueous phase by a high-speed mixer. The resulting mixture isemulsified until the emulsion viscosity increases to more than 200 cP.The resulting water-in-oil emulsion is charged into a glass-jacketedkettle, which was equipped with a paddle stirrer and thermometer. Theemulsion was purged with nitrogen for 30 minutes to remove oxygen. Next,0.01 parts AIBN as an initiator were added to the emulsion. Thetemperature was increased from room temperature to 40° C. in 30 minutes.The polymerization was allowed to proceed for 3 hours at 40° C. Thereaction proceeded for another hour at 50° C. The temperature was thenkept at 70° C. for one more hour. Dropwise, 2 wt. % of a linear alcoholethoxylate inverting surfactant containing 12-15 carbon units and havingan HLB of 13.3 was slowly added to the emulsion.

Example 3—FR 3 (Paraffin Base Oil, Salt Tolerant Monomers)

A terpolymer of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS),acrylamide (AM) and acrylic acid (AA) invert emulsion were prepared by asimilar method to Example 1, except with the use of paraffin oil inplace of BIO-BASE® oil. The oil phase is made by mixing 20 partsparaffin oil, with 2 parts emulsifier, which is made by mixing Span® 60with Tween® 61 surfactant that provided an HLB of 6.5. The resulting oilphase is mixed by an overhead mixer and a clear oil phase solution isready for emulsification. The aqueous phase is made by mixing 20 partsAM, 2 parts AMPS, 8 parts AA, and 40 parts water. The pH of the aqueoussolution was adjusted to pH 6-8 by adding sodium hydroxide. The oilphase was mixed with the aqueous phase using a high-speed mixer. Theresulting mixture was emulsified until the emulsion viscosity increasedto more than 200 cP. The resulting water-in-oil emulsion was chargedinto a glass-jacketed kettle equipped with a paddle stirrer andthermometer. The emulsion was purged with nitrogen for 30 minutes toremove oxygen. Then, 0.01 parts AIBN as an initiator was added to theemulsion. The temperature was increased from room temperature to 40° C.in 30 minutes. The polymerization was allowed to proceed for 3 hours at40° C. The reaction was allowed to proceed for another hour at 50° C.The temperature was then kept at 70° C. for one more hour. Dropwise, 2wt. % of a linear alcohol ethoxylate inverting surfactant containing12-15 carbon units and having an HLB of 13.3 was slowly added to theemulsion.

Example 4—FR 4 (Paraffin Base Oil, No Salt Tolerant Monomers)

A copolymer of acrylamide (AM) and acrylic acid (AA) invert emulsion isprepared by a similar method as in Example 2 except with the use ofparaffin oil instead of BIO-BASE®. The oil phase was made by mixing 20parts paraffin oil with 2 parts emulsifier, which is made by mixingSpan® 60 with Tween® 61 surfactant that provided an HLB of 6.5. Theresulting oil phase was mixed by an overhead mixer and a clear oil phasesolution is ready for emulsification. The aqueous phase was made bymixing 20 parts AM, 10 parts AA, and 40 parts water. The pH of theaqueous solution was adjusted to pH 6-8 by adding sodium hydroxide. Theoil phase was mixed with the aqueous phase by a high-speed mixer. Theresulting mixture was emulsified until the emulsion viscosity increasedto more than 200 cP. The resulting water-in-oil emulsion was chargedinto a glass jacketed kettle equipped with a paddle stirrer andthermometer. The emulsion was purged with nitrogen for 30 minutes toremove oxygen. Next, 0.01 parts AIBN as an initiator was added to theemulsion. The temperature was increased from room temperature to 40° C.in 30 minutes. The polymerization was allowed to proceed for 3 hours at40° C. The reaction was allowed to proceed for another hour at 50° C.The temperature is kept at 70° C. for one more hour. Dropwise, 2 wt. %of a linear alcohol ethoxylate inverting surfactant containing 12-15carbon units and having an HLB of 13.3, is slowly added to the emulsion.

Example 5—Equipment

In an embodiment, the new friction reducer was synthesized using theequipment depicted in FIG. 4. Oil and surfactants were added firstly andmonomers, water, and NaOH were added followed the oil. Synthesized oilprovided the environmentally friendly aspect of the friction reducer.The optimized monomers provided the salt tolerant feature. The overalloptimized formulation provided ultimate friction reduction performancein both fresh water and harsh brine conditions

Example 6—Testing

To evaluate performance, friction reducer emulsion samples 1-4 (FR1-FR4)were tested on a Chandler Flow-loop equipped with ½″ or ¾″ OD pipe. Thetests were performed at a rate of 8 gallons per minute. The ½″ tuberesults are shown in FIG. 1-FIG. 3. All of products were tested inHouston tap water (HTW). Selected products were also tested in 1.4 g/mlsodium bromide solution. Other products were also tested in sodiumnitrate and sodium chloride solutions for their salt toleranceperformance.

The four friction reducers produced in Examples 1-4 were tested in HTWwith 0.25 GPT dosage (0.025%). From FIG. 1, it can be seen that thefriction reducer products with BIO-BASE® oil (FR1, FR2) have much betterperformance than the conventional paraffin oil-based friction reducerproducts (FR3, FR4). FR1 and FR2 hydrate immediately when added to waterand can reach maximum performance in a few seconds. FR1 and FR2 havesimilar performance in fresh water. Both exhibit around 78% frictionreduction with a 0.025% dosage. The conventional friction reducerproducts based on paraffin oil (FR3, FR4) only have exhibit about 56%maximum friction reduction with a 0.025% dosage. Further, it takes 3-6minutes for FR3 and FR4 to reach their maximum performance.

The hydrofracture fluid only takes a few minutes to travel through thewellbore to reach the formation. If the hydration time is longer thanthis time, the friction reducer will not be effective. For this reasonand for comparison, the new friction reducers disclosed herein, based onBIOBASE® oil, are much better than conventional friction reducers.Another criterion with which to evaluate friction reducers is the shearstability. In practice, the fracturing fluid is pumped at high speed andthe chemicals in the fluid are under high shearing forces. As indicatedin FIG. 1, both FR1 and FR2 are quietly stable during the whole test.Only a few percentages decrease of friction reduction is indicated. BothFR1 and FR2 have excellent performance in fresh water fluid.

To evaluate the performance of BIO-BASE oil friction reducer in weightedbrine, both FR1 and FR2 were tested at 1.4 g/ml sodium bromide solutionas shown in FIG. 2. Sodium bromide is widely used in hydrofracturing toincrease the density of fracturing fluid. Saturated sodium bromide wasused to maximally increase the density of the fluid. The saturatedsodium bromide caused the conventional friction reducer failure problem.Both FR1 and FR2 are synthesized using BIO-BASE® oil as continuousphase. Their performance is quite different in comparison with theconventional friction reducer. FR1 can reach around 75% maximum frictionreduction. FR2 can only reach to 65% maximum friction reduction. It canbe concluded that the FR1 is much more salt tolerant due to the salttolerant monomer component. Both FR1 and FR2 hydrate quickly and havevery good shear stability. FR1 shows a small decrease after a fewminutes. FR2, which gives less friction reduction, shows excellentperformance on shear behavior.

In FIG. 3, salt tolerant FR1 was also test in a saturated sodium nitratesolution. Saturated sodium nitrate solution is another cheaper optionfor weighted fracturing fluid. The conventional friction reducerperformance is very bad in this situation due to ionic interaction. FR1was tested in saturated sodium nitrate and shows excellent results. Evenwith a 0.25 GPT dosage, the friction reduction can reach 69%. When thedosage increased to 0.5 GPT, the friction reduction can be as high as74%. In both situations, the product can be hydrated in a few seconds,which is very fast.

The base oil used in FR1 and FR2 is a synthetic hydrocarbon fluid whichis derived from natural gas through a gas-to-liquids (GTL) process. Itprovides excellent performance for FR1 and FR2 and has a favorableenvironmental profile. BIO-BASE® oil has a low viscosity to providebetter performance in low temperatures, improved friction reductionefficiency, and increases the inversion speed. Bio-based oil is readilybiodegradable, does not bioaccumulate, is non-toxic, and has an OffshoreChemical Notification Scheme for the North Sea (OCNS) ranking of group E(lowest environmental hazard). The ASTM 5790 modified testing methodindicated non-detectable benzene, toluene, ethylbenzene, and xylene(BTEX). Biodegradation research showed that BIO-BASE® oil can degrade75% within 28 days in freshwater according to the Organization forEconomic Cooperation and Development 301F (OECD 301F). OECD 301F is asolutions biodegradation test that determines the biodegradability bymeasuring consumption of oxygen. The biodegradation study in marinewater showed that the BIO-BASE® oil can degrade 62% within 28 days byOrganization for Economic Cooperation and Development 306 (OECD 306).OECD 306 measures biodegradability in seawater by two methods, the shakeflask method and the closed bottle method. The inverting surfactant usedherein is also readily biodegradable. Therefore, the final emulsion isenvironmentally friendly.

All of the compositions and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the compositions and methods of this disclosure havebeen described in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to thecompositions and methods and in the steps or in the sequence of steps ofthe methods described herein without departing from the concept, spiritand scope of the disclosure. More specifically, it will be apparent thatcertain agents which are chemically related may be substituted for theagents described herein while the same or similar results would beachieved. All such similar substitutes and modifications apparent tothose skilled in the art are deemed to be within the spirit, scope andconcept of the disclosure as defined by the appended claims.

What is claimed is:
 1. A composition for a friction reducer for awellbore comprising an oil phase comprising about 10-70 partsgas-to-liquid synthesized base oil and about 1-20 parts emulsifiercomprised of sorbitan fatty acid ester and a ethoxylated sorbitan fattyacid ester surfactant; an aqueous phase comprising about 5-35 partsmonomers comprising acrylamide (AM),2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), acrylic acid (AA),and water; and about 0.001 to 1 parts of an initiator selected from thegroup comprising ammonium peroxodisulfate, tert-butyl hydroperoxide,dimethane sulfonyl peroxide, potassium persulfate, benzoyl peroxide,lauroyl peroxide, sodium persulfate, 2,2′-Azobis(isobutyronitrile),2,2′-Azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-Azobis(2,4-dimethylvaleronitrile), Dimethyl2,2′-azobis(2-methylpropionate), 2,2′-Azobis(2-methylbutyronitrile),1,1′-Azobis(cyclohexane-1-carbonitrile),2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride,2,2′-Azobis(2-methylpropionamidine)dihydrochloride,2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate,diethyl 2,2′-azobisisobutyrate, dimethyl 2,2′-azobisisobutyrate,2-methyl 2′-ethyl azobisisobutyrate, dimethyl 2,2′-azobis(isobutyrate),2,2′-Azobis[2-(2-imidazolin-2-yl)propane],2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide],4,4′-Azobis(4-cyanovaleric acid), or combinations thereof.
 2. Thecomposition of claim 1 wherein the amount of the gas-to-liquidsynthesized base oil is about 20 parts.
 3. The composition of claim 1wherein the emulsifier is sorbitan monostearate and sorbitan fatty acidester ethoxylate surfactant and the amount of the emulsifier is about 2parts.
 4. The composition of claim 1 wherein the amount of the AM isabout 20 parts, the amount of the AMPS is about 2 parts, and the amountof the AA is about 8 parts.
 5. The composition of claim 1 wherein theamount of the water is about 40 parts.
 6. The composition of claim 1wherein the initiator is 2,2′-Azobis(isobutyronitrile) and the amount ofthe 2,2′-Azobis(isobutyronitrile) is about 0.01 parts.
 7. Thecomposition of claim 1 wherein the pH of the aqueous solution is 6-8. 8.The composition of claim 1 further comprising a surfactant with an HLBof at least about 10 at about 2 wt. %.
 9. A method of preparing afriction reducer for a wellbore comprising preparing an oil phase bymixing about 10-70 parts gas-to-liquid synthesized base oil with about1-20 parts emulsifier comprising sorbitan monostearate and sorbitanfatty acid ester ethoxylate surfactant; mixing the resulting oil phaseuntil it is clear; preparing an aqueous phase comprising about 5-35parts of monomers comprising mixing an AM, an AMPS, an AA, and a waterand adjusting the pH to 6-8; mixing the oil phase with the aqueous phaseto form a mixture; emulsifying the resulting mixture to form an emulsionwith a viscosity of greater than 200 cP; purging the emulsion withnitrogen for 30 minutes; adding about 0.001-1 parts an initiatorselected from the group comprising ammonium peroxodisulfate, tert-butylhydroperoxide, dimethane sulfonyl peroxide, potassium persulfate,benzoyl peroxide, lauroyl peroxide, sodium persulfate,2,2′-Azobis(isobutyronitrile),2,2′-Azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-Azobis(2,4-dimethylvaleronitrile), Dimethyl2,2′-azobis(2-methylpropionate), 2,2′-Azobis(2-methylbutyronitrile),1,1′-Azobis(cyclohexane-1-carbonitrile),2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride,2,2′-Azobis(2-methylpropionamidine)dihydrochloride,2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate,diethyl 2,2′-azobisisobutyrate, dimethyl 2,2′-azobisisobutyrate,2-methyl 2′-ethyl azobisisobutyrate, dimethyl 2,2′-azobis(isobutyrate),2,2′-Azobis[2-(2-imidazolin-2-yl)propane],2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide],4,4′-Azobis(4-cyanovaleric acid), or combinations thereof to theemulsion; increasing a temperature of the emulsion from room temperatureto 40° C. over a period of about 30 minutes; incubating the emulsion forabout 3 hours at 40° C.; incubating the emulsion for about 1 hour at 50°C.; and incubating the emulsion for about 1 hour at 70° C.
 10. Themethod of preparing of claim 9 further comprising charging the emulsioninto a glass-jacketed kettle equipped with a paddle stirrer andthermometer.
 11. The method of preparing of claim 9 wherein the amountof the gas-to-liquid synthesized base oil is about 20 parts.
 12. Themethod of preparing of claim 9 wherein the emulsifier is sorbitanmonostearate and a sorbitan fatty acid ester ethoxylate surfactant andthe amount of the emulsifier is about 2 parts.
 13. The method ofpreparing of claim 9 wherein the amount of the AM is about 20 parts, theamount of the AMPS is about 2 parts, and the amount of the AA is about 8parts.
 14. The method of preparing of claim 9 wherein the amount of thewater is about 40 parts
 15. The method of preparing of claim 9 whereinthe initiator is 2,2′-Azobis(isobutyronitrile) and the amount of the2,2′-Azobis(isobutyronitrile) is about 0.01 parts.
 16. The method ofpreparing of claim 9 further comprising adding a surfactant with an HLBof at least about 10 at about 2 wt. %.
 17. A method of use comprisingpumping at high speed the composition of claim 1 into a wellbore. 18.The method of use of claim 17 wherein the composition reduces friction.19. The method of use of claim 17 wherein the composition is salttolerant.
 20. The method of use of claim 17 wherein the composition isbiodegradable.